Lewis Short
(adverb) : prīmĭtus, id.
* At first, originally, for the first time (ante- and post-class. and poet.): primitu', Lucil. ap. Non. 154, 29: primitus cum exit vitis,Varr. R. R. 1, 31, 2: primitus oritur herba,id. ib. 2, 2, 14; Verg. Cir. 490; Cat. 19, 10: primitus enim ex libamentis deos placabant,Val. Max. 2, 5, 5: proinde atque si primitus Latine fictum esset,Gell. 1, 18, 1; Amm. 14, 6, 12.
Charlton T. Lewis, Charles Short, A Latin Dictionary